The Leica Cap for Hood of M Lens is used to protect your camera’s lens from rain and unintentional finger prints.The Leica Lens Cap can fit 35 mm f1.4M, 21mm f/2.8, 24mm f/2.8, 35mm F2.0 Aspherical Lens, and 35mm F1.4 M Aspherical M-LensesIt is essential to use the Leica Lens Cap as you can protect your camera’s lens from stray light and irradiation